The present invention relates to conversion of moving picture format for video signal transfer, storage and displaying. Particularly, this invention relates to conversion of interlaced video signals to other interlaced video signals with different scanning lines.
Digital moving picture video signals are classified into video formats as shown in TABLE 1 with difference in scanning type (SP), the number of effective scanning lines (ESL), frame/field picture rate (PR), the number of pixels in the horizontal direction (PH) and picture aspect ratio (PAR).
As shown in TABLE 1, the video formats define two scanning types, interlaced (i) and progressive (p) scanning; the number of scanning lines (in one frame for interlaced scanning), 480 for NTSC, and 720 or 1080 for HDTV; and picture rate, 60 Hz (accurately, 59.64 Hz) for interlaced scanning, and 24 or 30 Hz (like films) for progressive scanning.
The video formats as described above are converted to each other with conversion of, such as, picture rate, scanning type, and the number of scanning lines and pixels in the horizontal direction.
Conversion of interlaced video signals to other interlaced video signals with the same picture rate require conversion of only the number of scanning lines and pixels in the horizontal direction. The number of scanning lines is converted to another per filed or frame for interlaced video signals with the same picture rate.
This scanning line conversion offers high resolution only in the vertical direction for field video signals. Such scanning line conversion also offers high resolution for still pictures of frame video signals. Moving pictures of frame video signals are however degraded drastically due to blurs or double images because even and odd fields at different moments overlap each other.
Conversion of, for example, interlaced moving picture signals of 480 scanning lines (480i-format interlaced moving picture signals) to interlaced moving picture signals of 1080 scanning lines (1080i-format interlaced moving picture signals) are performed as follows:
The number of scanning lines of the 480i-format interlaced moving picture signals is converted into 1080.
Each of the even and odd fields with 240 scanning lines is converted by re-sampling (over-sampling) into another with 540 scanning lines for one field of 1080i-format.
The number of scanning lines is increased to 540, however, the resolution of each field lowers to about 120 cph (cycle per height) which is the resolution of field video signals.
Frames of 480 scanning lines are also converted into other frames with 1080 scanning lines. Such conversion of still picture frames offers resolution of about 180 cph, however, movement of the still picture frames degrades their picture quality.
Each converted frame or field of 720 pixels is converted into frame or filed of 1920 pixels by re-sampling (over-sampling) to have a 1080i-format interlaced moving picture signal. The number of pixels is increased with no change in resolution.
The video format conversion described so far offers a low resolution which corresponds to a field of the original moving picture signals (480i-format interlaced moving picture signals in the example) when the number of scanning lines is converted per field. Aliasing components of each interlaced field video signal remain unchanged after conversion.
Such conversion per frame offers high resolution for still pictures, however, movement of the still pictures degrades picture quality due to blurs or double images as discussed above.
Video format conversion per frame or field as described above degrades the quality of converted pictures compared to pictures before conversion.
A purpose of the present invention is to provide an apparatus and a method of video format conversion with high resolution but few aliasing components.
The present invention provides a moving picture format conversion apparatus for converting a first interlaced video signal of a first number of scanning lines into a second interlaced video signal of a second number of scanning lines, the first and second numbers being different from each other.
The apparatus includes a progressive video converter to convert the first interlaced video signal into a first progressive video signal of the first number of scanning lines by interpolating the first interlaced video signal with scanning lines which have been decimated from the first interlaced video signal; a scanning line converter to convert the first number of scanning lines of the first progressive video signal into the second number of scanning lines by re-sampling, to generate a second progressive video signal of the second number of scanning lines; and an interlaced video converter to convert the second progressive video signal into the second interlaced video signal by decimating the second number of scanning lines of the second progressive video signal.
There are alternatives for the scanning line converter for generating the second progressive video signal and the interlaced video converter for converting the second progressive video signal into the second interlaced video signal. The apparatus may include another scanning line converter to convert one of an even and odd frame of the first progressive video signal into an even field of the second interlaced video signal and the other of the even and odd frames of the first progressive video signal into an odd field of the second interlaced video signal; and an interlaced video composer to combine the even and odd fields to compose the second interlaced video signal.
Moreover, the present invention provides a moving picture format conversion method of converting a first interlaced video signal of a first number of scanning lines into a second interlaced video signal of a second number of scanning lines, the first and second numbers being different from each other.
The first interlaced video signal is converted into a first progressive video signal of the first number of scanning lines by interpolating the first interlaced video signal with scanning lines which have been decimated from the first interlaced video signal. The first number of scanning lines of the first progressive video signal is converted into the second number of scanning lines by re-sampling, to generate a second progressive video signal of the second number of scanning lines. And, the second progressive video signal is converted into the second interlaced video signal by decimating the second number of scanning lines of the second progressive video signal.
There are alternatives for conversion of the first number of scanning lines of the first progressive video signal for generation of the second progressive video signal; and conversion of the second progressive video signal into the second interlaced video signal. One of an even and odd frame of the first progressive video signal may be converted into an even field of the second interlaced video signal and the other of the even and odd frames of may be converted into an even field of the second interlaced video signal and the other of the even and odd frames of the first progressive video signal may be converted into an odd field of the second interlaced video signal. And, the even and odd fields are combined to compose the second interlaced video signal.